Pumping system and method for injecting a mixture of liquids into a subterranean formation

ABSTRACT

A system and method to inject a combined hydrocarbon-based liquid stream and a liquid carbon dioxide stream into a subterranean formation via a well using a single high-pressure pump.

RELATED INVENTION

This is a divisional of application Ser. No.: 11/501,570 filed on Aug.9, 2006 now U.S. Pat. No. 7,513,307.

This invention is entitled to and hereby claims the benefit of thefiling date of Provisional Patent Application Serial No. 60/766,815filed Feb. 13, 2006 by Randal L. Decker entitled “Liquid CO₂ EmulsionPumping System.”

FIELD OF THE INVENTION

The present invention relates to an efficient injection system forinjecting a combined aqueous or hydrocarbon-based liquid stream and aliquid carbon dioxide stream via a well into a subterranean formation.

BACKGROUND OF THE INVENTION

In the use of liquid carbon dioxide for injection with various liquidwell treating materials, it has been necessary in the past to use twohigh-pressure pumps; one for the injection of an aqueous orhydrocarbon-based liquid stream and one for the liquid carbon dioxidestream to achieve the required injection and mixing pressures.

These high-pressure pumps, which are large pumps, are typically mountedon heavy duty trucks for movement to a well area. These pumps aretypically massive, positive displacement pumps having one or multipleplungers and are used to increase the pressure of injection streams to apressure suitable for injection into a well up to and at or exceedingfracturing conditions as required. The use of these pumps is expensivesince they are subject to a substantial per diem charge as a result ofthe high cost of the pumps and because such pumps have relatively highmaintenance costs.

Accordingly, a more efficient and economical way to inject a stream ofliquid carbon dioxide and a liquid stream of aqueous orhydrocarbon-based liquid treating solution into a well at a suitablepressure has been sought.

SUMMARY OF THE INVENTION

The invention comprises a system for efficient injection of a combinedhydrocarbon-based liquid stream and a liquid carbon dioxide stream intoa well penetrating a subterranean formation; the system consistingessentially of: a liquid booster pump in fluid communication with asource of an aqueous or hydrocarbon-based liquid and effective toincrease a pressure in a liquid stream of the hydrocarbon-based liquidto a first selected pressure; a liquid carbon dioxide booster pump influid communication with a source of liquid carbon dioxide and effectiveto increase a pressure in a stream of liquid carbon dioxide to a secondselected pressure; and, a high-pressure pump in fluid communication withthe liquid booster pump and the liquid carbon dioxide booster pump andadapted to receive and combine the liquid stream of hydrocarbon-basedliquid and the stream of liquid carbon dioxide and increase a pressureof the combined stream to a pressure suitable for injection into thewell.

The invention further comprises a method for injection of a combinedhydrocarbon-based liquid stream and a liquid carbon dioxide stream intoa well penetrating a subterranean formation, the method consistingessentially of: increasing the pressure of the hydrocarbon-based liquidstream to 550 psia, up to 650 psia, in a liquid booster pump; increasingthe pressure of a stream of liquid carbon dioxide to about 550 psia, upto 650, psia in a liquid carbon dioxide booster pump; and, passing theliquid carbon dioxide stream and the hydrocarbon-based liquid stream toa high-pressure pump wherein the streams are combined and wherein thepressure of the combined streams is increased to a pressure sufficientto inject the combined streams into the well.

The invention further comprises a method for injection of a combinedhydrocarbon-based liquid stream and a liquid carbon dioxide stream intoa subterranean formation via a well by passing the combined aqueous orhydrocarbon-based liquid stream and the liquid carbon dioxide stream toa high-pressure pump where the liquid streams are combined and whereinthe pressure of the combined streams is increased to a pressure greaterthan 650 psia.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a prior art system for injecting amixture of a treating solution and carbon dioxide; and,

FIG. 2 shows a schematic diagram of an embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the discussion of the Figures and embodiments, various features suchas pumps, valves and the like necessary to achieve the flows requiredand discussed have not been shown for simplicity since such features areconsidered to be well known to those skilled in the art.

A prior art system 10 is shown in FIG. 1.

In FIG. 1 a hydrocarbon-based liquid source is shown as an HCL transport12 and a hydrocarbon-based additive is shown as a corrosion inhibitortransport 16. These transports are typically large tanker trucks or thelike which can be moved to a well site for treatment of the well.Typically these are trucks which discharge their cargos at a pressurefrom atmospheric pressure, to a booster pump (not shown) that increasesthe liquid pressure to about 50-150 psia as shown with the solvent andcorrosion inhibitor solution being passed through lines 14 and 18 to ahigh-pressure triplex pump 20. The high-pressure pump 20 increases thepressure of the streams to a pressure sufficient for discharge into awell 24 via a line 22.

Liquid carbon dioxide is typically delivered by trucks, shown as CO2transports 26 (CO₂ transports) and is typically supplied at about250-300 psia pressure. The carbon dioxide is typically passed to aliquid carbon dioxide booster pump 32 through one of lines 28 and 30.Booster pump 32 increases the pressure of the liquid carbon dioxidestream by about 50 to about 75 psia and passes it via a line 34 to ahigh-pressure triplex pump 36 which increases the pressure of the carbondioxide stream and discharges the liquid carbon dioxide stream through aline 38 to well 24. The streams are mixed in well 24 as they passdownwardly through the well.

In FIG. 2 a schematic diagram of an embodiment 100 of the presentinvention is shown wherein hydrocarbon-based liquid is stored atatmospheric pressure in a vessel 102. The liquid carbon dioxide isstored at 250-300 psia. In this embodiment, liquid carbon dioxide isstored in a vessel 124 (CO₂ storage) and is produced through a line 126and passed through a vapor separator 136 and then through a line 138 toa CO2 booster pump 140 where it is compressed to a pressure from about550 psia, up to about 600 psia. The stream compressed in booster pump140 is passed through a line 142 and then through a line 116 to ahigh-pressure triplex pump 118. The high-pressure pump then increasesthe pressure in this stream along with the hydrocarbon-based liquidstream for injection through a line 120 to a well 122.

The hydrocarbon-based liquid is stored in storage 102 and passed via aline 108 to a liquid booster pump 110 where its pressure is increased toa pressure of about 600 psia and then combined via a line 112 with thestream from line 142 and fed to a high-pressure pump 118 via line 116.Liquid booster pump 110 also is in fluid communication with a recycleloop comprising a line 112 and a line 114 so that the output from liquidbooster pump 110 can be recycled if desired in whole or in part forpressure and flow volume control.

Vapor separator 136 operates to remove accumulated vapor that has beenformed by the absorption of heat as the liquid carbon dioxide has beenmoved from storage 124 via line 126. The vapor is vented to theatmosphere from the top of separator 136, thereby preventing the boosterpump 140 and high-pressure pump 118 from cavitating. In the event thatthe liquid CO₂ rate must be reduced to pump 118, a portion of the streamin line 142 can be diverted through a line 144 and can be re-cycledthrough vapor separator 136 which will remove accumulated vapor and aidin controlling a liquid CO₂ pump 140 rate and pressure from pump 140 tohigh-pressure pump 118. The stream is then passed through a line 146back to line 142. This enables the operation of vapor separator 136 toseparate vapor from the liquid carbon dioxide as required. As indicated,it is contemplated that the vapor separator will contain only relativelysmall volumes of carbon dioxide vapor at any given time sincesubstantial amounts of carbon dioxide liquid are passing through thesevessels.

This embodiment allows the liquid carbon dioxide to be in storage at250-300 psia and allows for the hydrocarbon-based liquid to be instorage at atmospheric pressure. According to the present invention, thehydrocarbon-based solvent and the carbon dioxide are supplied to asingle high-pressure pump at a pressure of about 550 psia, up to 650psia, and at preferably about 600 psia. In the past it has beenconsidered necessary to have a high-pressure pump for each of thehydrocarbon-based liquid and the liquid carbon dioxide.

According to the present invention only a single high-pressure pump isused. This results in a substantial increase in the process efficiencysince better emulsification is achieved. It also results in asubstantial reduction of expense in that only one high-pressure pump isrequired to be maintained and operated on site. The resulting emulsionsare formed in the high-pressure pump and the emulsion is pumped into thewell at a pressure great than 650 psia.

While the invention has been discussed above by reference to aqueoushydrochloric acid as a treating solution, it should be understood thatthe acid solution may contain methanol and other additives. While thepresence of methanol is optional it is desirable in many instances thatthe methanol be present in an amount from about 5 to about 25 weightpercent in the treating liquid. Further the invention can be used toinject not only aqueous acid but alternatively hydrocarbon-based liquidssuch as organic solvents, scale inhibitors, corrosion inhibitors and thelike into the well. The only real limitation on the use of the treatingliquid is that it be liquid when mixed the liquid carbon dioxide.

As well known to those skilled in the art, whatever arrangement is usedto provide the liquid carbon dioxide to the high-pressure pump at thedesired pressure must maintain the liquid carbon dioxide under suitabletemperature and pressure conditions to maintain it in a liquid state.Such conditions are well known to those skilled in the art.

While the embodiments shown are preferred, it is considered necessaryfor the practice of the present invention that the carbon dioxide bedelivered in a liquid form at a pressure from about 550 psia, up to 650psia, to the high-pressure pump along with the aqueous solution whichmust be delivered at the same or a comparable pressure and at atemperature which does not result in vaporization of the liquid carbondioxide. These streams may be introduced in mixture or alone into thehigh-pressure pump. In either event the resulting emulsion is readilypumped by the high-pressure pump into the well as shown, for instance inFIG. 2, via line 120 into well 122.

As mentioned previously, the high-pressure pumps are typically large,positive displacement pumps having from 1 to 5 or more plungers whichare relatively high maintenance and high expense pumps for use becauseof their ability to generate the extreme pressures used in fracturingoperations and the like. These positive displacement pumps are suitableas the high-pressure pump in the present invention.

Multi-stage centrifugal pumps may be used for similar applications butare not typically used or preferred for fracturing operations. They aresuitable for use as the high-pressure pump in the present invention solong as they are capable of mixing the aqueous solution and the liquidcarbon dioxide and injecting the resulting mixture into a well at apressure greater than about 650 psia.

While typical and preferred operating conditions for the invention havebeen described above, the hydrocarbon-based liquid solution could bepassed to the high-pressure pump at a higher or lower pressure and thehigher-pressure pump is capable of compressing the mixture to pressuresmuch higher than 650 psia. The liquid booster pumps and the feed pumps,if used, may be centrifugal pumps, multi-stage centrifugal pumps and thelike as required to achieve the desired pressure increases. Theoperation of such pumps is much less expensive than for thehigh-pressure pumps and the maintenance requirements for such pumps aremuch lower. The preferred pressures discussed above may be varied solong as the liquid streams are mixed as liquids and so long as thecarbon dioxide is passed to the high pressure pump as a liquid.

By the present invention, the use of a second high-pressure pump hasbeen omitted and improved mixing and operational efficiency has beenachieved in the delivery of the treating liquid/liquid carbon dioxidemixture into the well.

While the present invention has been described by reference to certainof its preferred embodiments, it is pointed out that the embodimentsdescribed are illustrative rather than limiting in nature and that manyvariations and modifications are possible within the scope of thepresent invention. Many such variations and modifications may beconsidered obvious and desirable by those skilled in the art based upona review of the foregoing description of preferred embodiments.

1. A system for efficient injection of a combined hydrocarbon-basedliquid stream and a liquid carbon dioxide stream into a well penetratinga subterranean formation; the system consisting essentially of: a) aliquid booster pump in fluid communication with a source of ahydrocarbon-based liquid and effective to increase a pressure of a firstliquid stream to a first selected pressure; b) a carbon dioxide boosterpump in fluid communication with a source of liquid carbon dioxide andeffective to increase a pressure of a first stream of liquid carbondioxide to a second selected pressure; and, c) a high-pressure pump influid communication with the liquid booster pump and the carbon dioxidebooster pump and adapted to receive and combine the first liquid streamand the first stream of liquid carbon dioxide and increase a pressure ofthe combined stream to a pressure suitable for injection into the well.2. The system of claim 1 wherein the first selected pressure is fromabout 550 up to 650 psia.
 3. The system of claim 1 wherein the firstselected pressure is about 600 psia.
 4. The system of claim 1 whereinthe first selected pressure and the second selected pressure are aboutthe same.
 5. The system of claim 1 wherein the system includes a vaporseparator in fluid communication with the source of liquid carbondioxide and the carbon dioxide booster pump.
 6. The system of claim 1wherein the high-pressure pump is a positive displacement pump or amulti-phase centrifugal pump and wherein the high-pressure pump isadapted to produce a pressure of the combined stream greater than 650psia.
 7. The system of claim 6 wherein the high-pressure pump is apositive displacement pump.
 8. The system of claim 6 wherein thehigh-pressure pump is a multi-stage centrifugal pump.
 9. A method forinjection of a combined hydrocarbon-based liquid and a liquid carbondioxide stream into a well penetrating a subterranean formation, themethod consisting essentially of: a) increasing the pressure of ahydrocarbon-based liquid stream to about 550 up to 650 psia in a liquidbooster pump; b) increasing the pressure of a stream of liquid carbondioxide to a pressure from about 250 psia up to 650 psia in a carbondioxide booster pump; and, c) passing the liquid carbon dioxide streamand the hydrocarbon-based liquid stream to a high-pressure pump whereinthe streams are combined and wherein the pressure of the combinedstreams is increased to a pressure sufficient to inject the combinedstreams into the well.
 10. The method of claim 9 wherein thehydrocarbon-based liquid stream comprises a hydrocarbon-based solvent.11. The method of claim 9 wherein the stream of liquid carbon dioxideand the hydrocarbon-based liquid are passed to the high-pressure pump atabout the same pressure.
 12. The method of claim 9 wherein thehydrocarbon-based stream is selected from the group consisting of anorganic solvent, a scale inhibitor or a corrosion inhibitor.
 13. Themethod of claim 9 wherein the combined streams contain from about 5 toabout 95 weight percent carbon dioxide.
 14. The method of claim 9wherein the high-pressure pump is a positive displacement pump or amulti-phase centrifugal pump and wherein the high-pressure pump isadapted to produce a pressure of the combined stream greater than 650psia.
 15. The method of claim 9 wherein the high-pressure pump is apositive displacement pump.
 16. The method of claim 9 wherein thehigh-pressure pump is a multi-stage centrifugal pump.
 17. A method forefficient injection of a combined hydrocarbon-based liquid stream and aliquid carbon dioxide stream into a subterranean formation; the methodconsisting essentially of: a) passing the liquid hydrocarbon-basedstream to a high-pressure pump; b) passing the liquid carbon dioxidestream to the high-pressure pump; and, c) mixing the liquidhydrocarbon-based stream and the liquid carbon dioxide stream in thehigh-pressure pump to produce a combined liquid stream and increasingthe pressure of the combined liquid stream to a pressure sufficient forinjection into the subterranean formation.
 18. The method of claim 17wherein the high-pressure pump is a positive displacement pump or amulti-phase centrifugal pump and wherein the high-pressure pump isadapted to produce a pressure of the combined stream greater than 650psia.
 19. The method of claim 17 wherein the high-pressure pump is apositive displacement pump.